It is well-known that various articles of manufacture require or benefit from a heating or baking step during manufacture thereof. For example, many articles coated with as paint and/or other protective coatings are thereafter dried and/or cured in large ovens prior to final assembly and/or shipment. Such ovens are typically heated with hot air which flows into and out of the oven enclosure by means of ducts. It is common to heat by direct-firing, meaning that the products of the heat-producing combustion are injected directly into the oven air supply. Devices such as fans are often used to circulate air within the oven enclosure to equalize temperatures throughout the oven and to reduce the risk of explosion.
As the articles or the coatings on the articles within the oven dry, they typically release combustible and odiferous fumes which, if allowed to accumulate, may eventually cause the atmospheric composition with the oven enclosure to exceed tolerable levels or even to become explosive. To prevent this occurrence, the fume-laden atmosphere of the oven enclosure is cleared by means of an exhaust fan and diluted or replaced with fresh air. Even with partial recirculation, this gives rise to an increase in fuel comsumption to maintain a desired temperature level, and creates the potential for atmospheric pollution.
Even with the use of an exhaust system, the presence of corrosive fumes and high humidity from direct-fired heating within the oven enclosure can cause the inner liner and insulation of the oven enclosure to deteriorate rapidly. This deterioration, in turn, can produce the introduction of particulate contaminants into the oven enclosure, which contaminants can adversely effect the quality of the finish of the drying articles, especially if the particulate matter becomes airborne as a result of air currents within the oven enclosure. Filters in recirculation paths may, of course, be installed but installation and maintenance of filters add to cost.